In the PDF owner's handbook 2002 publication LRL 0545ENG it's in the "Driving and operating" chapter at the "transfer gearbox" -

OM - Diff lock.jpg
 
I can see the CDL inclusion in the Owners Handbook for the 03 model, which makes sense as it was an option for the later models. But I can see nothing in the handbooks for earlier models. Not sure why this would be if it was an option for 99-01 models.
 

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